NEAR Shoemaker
Mission type | Orbiter (433 Eros) |
---|---|
Operator | NASA · APL |
COSPAR ID | 1996-008A |
SATCAT no. | 23784 |
Website | Official website |
Mission duration | 5 years, 21 days |
Spacecraft properties | |
Launch mass | 805 kg[1] |
Dry mass | 487 kilograms (1,074 lb) |
Power | 1,800 W |
Start of mission | |
Launch date | February 17, 1996 Cape Canaveral LC-17B | 20:43:27
End of mission | |
Last contact | February 28, 2001 | ~00:00 UTC
Landing date | February 12, 2001 | 20:01 UTC
Landing site | South of Himeros crater, 433 Eros |
Flyby of 253 Mathilde | |
Closest approach | June 27, 1997 | 12:56 UTC
Distance | 1,212 kilometers (753 mi) |
433 Eros orbiter | |
Orbital insertion | February 14, 2000 | 15:33 UTC
Orbits | 230 orbits[2] |
Official insignia of the NEAR Shoemaker mission Discovery program → |
Near Earth Asteroid Rendezvous – Shoemaker (NEAR Shoemaker), renamed after its 1996 launch in honor of planetary scientist
The primary scientific objective of NEAR was to return data on the bulk properties, composition,
Development
NEAR was the first robotic
Mission profile
Summary
The mission's primary goal was to study the near-Earth asteroid 433 Eros from orbit for approximately one year. Eros is an S-type asteroid approximately 13 × 13 × 33 km in size, the second largest near-Earth asteroid. Initially, the orbit was circular with a radius of 200 km. The orbit radius was brought down in stages to a 50 × 50 km orbit on April 30, 2000, and decreased to 35 × 35 km on July 14, 2000. The orbit was raised over succeeding months to a 200 × 200 km orbit and then slowly decreased and altered to a 35 × 35 km retrograde orbit on December 13, 2000. The mission ended with a touchdown in Eros's "saddle" region on February 12, 2001.
Some scientists claim that the mission's ultimate goal was to link Eros, an asteroidal body, to meteorites recovered on Earth. With sufficient data on chemical composition, a causal link could be established between Eros and other S-type asteroids, and those meteorites believed to be pieces of S-type asteroids (perhaps Eros itself). Once this connection is established, meteorite material can be studied with large, complex, and evolving equipment, and the results can be extrapolated to bodies in space. NEAR did not prove or disprove this link to the satisfaction of scientists.
Between December 1999 and February 2001, NEAR used its gamma-ray spectrometer to detect
The journey to Mathilde
After launching on a Delta 7925-8 (a Delta II launch vehicle with nine strap-on solid-rocket boosters and a Star 48 (PAM-D) third stage) on February 17, 1996, and exited from Earth orbit, NEAR entered the first part of its cruise phase. NEAR spent most of the cruise phase in a minimal activity "hibernation" state, which ended a few days before the flyby of the 61 km diameter asteroid 253 Mathilde.[7]
On June 27, 1997, NEAR flew by Mathilde within 1200 km at 12:56 UT at 9.93 km/s, returning imaging and other instrument data. The flyby produced over 500 images, covering 60% of Mathilde's surface,[8] as well as gravitational data allowing calculations of Mathilde's dimensions and mass.[9]
The journey to Eros
On July 3, 1997, NEAR executed the first major deep space maneuver, a two-part burn of the main 450 N thruster. This decreased the velocity by 279 m/s and lowered
Failure of first attempt at orbital insertion
The first of four scheduled rendezvous burns was attempted on December 20, 1998, at 22:00 UT. The burn sequence was initiated but immediately aborted. The spacecraft subsequently entered
The original mission plan called for the four burns to be followed by an orbit insertion burn on January 10, 1999, but the abort of the first burn and loss of communication made this impossible. A new plan was put into effect in which NEAR flew by Eros on December 23, 1998, at 18:41:23 UT at a speed of 965 m/s and a distance of 3827 km from the center of mass of Eros. The camera took images of Eros, data were collected by the near IR spectrograph, and radio tracking was performed during the flyby. A rendezvous maneuver was performed on January 3, 1999, involving a thruster burn to match NEAR's orbital speed to that of Eros. A hydrazine thruster burn took place on January 20 to fine-tune the trajectory. On August 12, a two-minute thruster burn slowed the spacecraft velocity relative to Eros to 300 km/h.[7]
Orbital insertion
-
Trajectory graphic depicting the voyage of the NEAR spacecraft
-
Animation of NEAR Shoemaker's trajectory around Eros from April 1, 2000, to February 12, 2001
- NEAR Shoemaker
- 433 Eros
Orbits and landing
Following the flyby, NEAR moved to a 200 km circular orbit and shifted the orbit from
At 7 p.m. EST on February 28, 2001, the last data signals were received from NEAR Shoemaker before it was shut down. A final attempt to communicate with the spacecraft on December 10, 2002, was unsuccessful. This was likely due to the extreme −279 °F (−173 °C, 100 K) conditions the probe experienced while on Eros.[14]
Spacecraft and subsystems
Spacecraft
The spacecraft has the shape of an octagonal prism, approximately 1.7 m on a side, with four fixed
The craft was three-axis stabilized and used a single
Power was provided by four 1.8 by 1.2 meter
Spacecraft guidance was achieved through the use of a sensor suite of five digital solar attitude detectors, an inertial measurement unit (IMU), and a star tracker camera pointed opposite the instrument pointing direction. The IMU contained hemispherical resonators gyroscopes and accelerometers. Four reaction wheels (arranged so that any three can provide complete three-axis control) were used for normal attitude control. The thrusters were used to dump angular momentum from the reaction wheels, as well as for rapid slew and propulsive maneuvers. Attitude control was to 0.1 degree, line-of-sight pointing stability is within 50 microradians over one second, and post-processing attitude knowledge is to 50 microradians.[7]
The command and data handling subsystem was composed of two redundant command and telemetry processors and solid state recorders, a power switching unit, and an interface to two redundant 1553 standard data buses for communications with other subsystems. NEAR was the first APL spacecraft to use significant numbers of plastic encapsulated microcircuits (PEMs), and the first to use solid-state data recorders for mass storage—previous APL spacecraft used magnetic tape recorders or magnetic cores.[16]
The solid-state recorders are constructed from 16 Mbit
The NEAR mission was the first launch of NASA's Discovery Program, a series of small-scale spacecraft designed to proceed from development to flight in under three years for a cost of less than $150 million. The construction, launch, and 30-day cost for this mission is estimated at $122 million. The final total mission cost was $224 million, which consisted of $124.9 million for spacecraft development, $44.6 million for launch support and tracking, and $54.6 million for mission operations and data analysis.[2]
Scientific payload and experiments
The science payload includes:[17]
- The Multi-Spectral Imager (MSI), designed and built by the Johns Hopkins University Applied Physics Laboratory, provided visible images of the asteroid's surface.
- The NEAR IR Spectrograph (NIS) covers a 0.8 to 2.6-micrometer spectral range in 62 bins.
- A three-axis fluxgate magnetometer supplied by NASA's Goddard Space Flight Center can measure the asteroid's magnetic field from DC to 10 Hz.
- The X-ray/Gamma-Ray Spectrometer (XGRS) is two instruments. The x-ray spectrometer measures x-ray fluorescence on the asteroid excited by solar flare x-rays. The gamma-ray spectrometer is a NaI scintillator with an active BGO shield.
- The laser rangefinder (NLR) is a direct-detection single-pulse rangefinder.
References
- ^ "NEAR Shoemaker". NASA's Solar System Exploration website. Retrieved December 1, 2022.
- ^ Applied Physics Lab.
- ^ a b "NEAR Shoemaker". NASA. Retrieved April 26, 2021.
- S2CID 109108852. Retrieved November 16, 2022.
- ^ a b c d Extended-mission opportunities for a Discovery-class asteroid rendezvous mission
- ^ .
- ^ a b c d e f g h "NEAR Shoemaker". NASA Space Science Data Coordinated Archive. Retrieved February 5, 2019.
- ^ Williams, David R. (December 18, 2001). "NEAR Flyby of Asteroid 253 Mathilde". NASA. Retrieved August 10, 2006.
- PMID 9405343. Retrieved August 29, 2007.
- ^ "The NEAR Rendezvous Burn Anomaly of December 1998" (PDF). Final Report of the NEAR Anomaly Review Board. November 1999. Archived (PDF) from the original on October 9, 2022. Retrieved February 2, 2017.
- ^ "Final Images from 2001 Feb 12". near.jhuapl.edu. Retrieved April 17, 2022.
- LCCN 2017059404. SP2018-4041. Archived(PDF) from the original on October 9, 2022.
- Applied Physics Lab.
- ^ "'NEAR Shoemaker's Silent Treatment". Applied Physics Laboratory. February 23, 2001.
- ^ Williams, David R. (February 8, 2000). "NEAR Mission Profile". NASA Goddard Space Flight Center. Retrieved February 5, 2019.
- ^ Ronald K. Burek. "The NEAR Solid-State Data Recorders". Johns Hopkins APL Technical Digest. 1998
- ^ Santo, A. G.; Lee, S. C.; Gold, R. E. (1995). "NEAR spacecraft and instrumentation". Journal of the Astronautical Sciences. 43 (4): 373–397.
- Text adapted from public domain NASA webpage.
- Trombka JI; Squyres SW; Bruckner J; Boynton WV; et al. (2000). "The elemental composition of asteroid 433 Eros: Results of the NEAR-Shoemaker x-ray spectrometer". Science. 289 (5487): 2101–2105. S2CID 29691912.
- Zuber MT; Smith DE; Cheng AF; Garvin JB; et al. (2000). "The shape of 433 Eros from the NEAR-Shoemaker Laser Rangefinder". Science. 289 (5487): 2097–2101. S2CID 20553832.
- Yeomans DK; Antreasian PG; Barriot JP; Chesley SR; et al. (2000). "Radio science results during the NEAR-Shoemaker spacecraft rendezvous with Eros". Science. 289 (5487): 2085–2088. PMID 11000104.
This article incorporates public domain material from websites or documents of the
External links
- NEAR Shoemaker Profile by NASA's Solar System Exploration
- NSSDC Master Catalog: Spacecraft – NEAR Shoemaker
- NASA GSFC: NEAR Shoemaker, Near Earth Asteroid Rendezvous
- Official NEAR Mission Site (Johns Hopkins Applied Physics Laboratory)
- Near Earth Asteroid Rendezvous
- NEAR Mission Archive at the NASA Planetary Data System, Small Bodies Node